title: Effects of intraduodenal lipid and protein on gut motility and hormone release, glycemia, appetite, and energy intake in lean men.
abstract: BACKGROUND
  Intraduodenal lipid modulates gastrointestinal motility and hormone release and suppresses energy intake (EI) more than does intraduodenal glucose. Oral protein is the most satiating macronutrient and modulates postprandial glycemia; the comparative effects of intraduodenal protein and lipid and their combined effects are unclear.
  
  
  OBJECTIVE
  We investigated the effects of intraduodenal protein and lipid, alone or in combination, on antropyloroduodenal motility, gastrointestinal hormone release, glycemia, and EI.
  
  
  METHODS
  Twenty lean men were studied on 5 randomized, double-blind occasions. Antropyloroduodenal motility, cholecystokinin, glucagon-like peptide-1 (GLP-1), insulin, glucagon, blood glucose, appetite, and nausea were measured during 90-min isocaloric (3 kcal/min) intraduodenal infusions of lipid [pure lipid condition (L3)], protein [pure protein condition (P3)], a 2:1 combination of lipid and protein [2:1 lipid:protein condition (L2P1)], a 1:2 combination of lipid and protein [1:2 lipid:protein condition (L1P2)], or a control. Immediately after the infusion, EI from a buffet lunch was quantified.
  
  
  RESULTS
  In comparison with the control, all nutrient infusions suppressed antral and duodenal and stimulated pyloric pressures (P < 0.05). Cholecystokinin and GLP-1 release and pyloric stimulation were lipid-load dependent (r ≥ 0.39, P < 0.01), insulin and glucagon releases were protein-load dependent (r = 0.83, P < 0.001), and normoglycemia was maintained. L3 but not P3 increased nausea (P < 0.05). Compared with the control, L3 and P3 but not L2P1 or L1P2 suppressed EI (P < 0.05) without major effects on appetite.
  
  
  CONCLUSIONS
  In lean men, despite differing effects on gut function, intraduodenal lipid and protein produce comparable reductions in energy intake. The effects of lipid may be a result of nausea. Protein also regulates blood glucose by stimulating insulin and glucagon. In contrast, at the loads selected, lipid:protein combinations did not suppress energy intake, suggesting that a threshold load is required to elicit effects. This trial was registered at Australia and New Zealand Clinical Trial Registry (http://www.anzctr.org.au) as 12609000949280.
authors.affiliation: University of Adelaide Discipline of Medicine and National Health and Medical Research Council of Australia Centre of Research Excellence in Translating Nutritional Science to Good Health, University of Adelaide, Adelaide, Australia.
authors.forename: Amy T
authors.initials: AT
authors.lastname: Ryan
authors.forename: Natalie D
authors.initials: ND
authors.lastname: Luscombe-Marsh
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Saies
authors.forename: Tanya J
authors.initials: TJ
authors.lastname: Little
authors.forename: Scott
authors.initials: S
authors.lastname: Standfield
authors.forename: Michael
authors.initials: M
authors.lastname: Horowitz
authors.forename: Christine
authors.initials: C
authors.lastname: Feinle-Bisset
mesh_terms: D000293:Adolescent; D000328:Adult; D001066:Appetite / Q000502:physiology*; D001786:Blood Glucose / Q000502:physiology*; D015992:Body Mass Index; D002766:Cholecystokinin / Q000097:blood; D018592:Cross-Over Studies; D004041:Dietary Fats / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D004311:Double-Blind Method; D002149:Energy Intake; D005768:Gastrointestinal Hormones / Q000097:blood; D005769:Gastrointestinal Motility; D041981:Gastrointestinal Tract / Q000502:physiology; D005934:Glucagon / Q000097:blood; D052216:Glucagon-Like Peptide 1 / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D008875:Middle Aged; D009520:New Zealand; D019518:Postprandial Period; D012527:Satiation; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D004041:Dietary Fats; D004044:Dietary Proteins; D005768:Gastrointestinal Hormones; D007328:Insulin; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D002766:Cholecystokinin